1. Field of the Invention
The present invention relates to a photographic film cassette and light-trapping members for the same, and more particularly to a cassette wherein rotation of a spool advances a leader of the photographic film to the outside of the cassette shell.
2. Description of the Related Art
Presently, a photographic film cassette (hereinafter referred to as cassette) containing a roll of 135-type (35 mm wide) photographic filmstrip (hereinafter referred to as film) is widely used. This cassette is constituted by a light-tight cassette shell provided with a passage mouth, a spool rotatably contained in the cassette shell, and photographic film wound on the spool. A pair of light-trapping ribbons (commonly called plush in the field of photography) constituted of strips of fabric are attached inside the passage mouth in order to prevent light from entering through the passage mouth into the cassette shell.
A number of different light-trapping ribbons are known to be effective, including a woven fabric, like velvet, with pile threads woven on its ground as described in Japanese Utility Model Publication No. 37-21388, a knitted fabric with pile threads knitted on its ground as described in Japanese Utility Model Publication No. 61-34526, a set of pile threads planted directly on faces in a passageway for the photographic film as disclosed in Japanese Utility Model Publication no. 37-4453 and Japanese Patent Laid-open Publication Nos. 53-105222 and 57-190948, and a non-woven fiber sheet as disclosed in Japanese Utility Model Laid-open Publication No. 51-127737.
As described in U.S. Pat. Nos. 4,832,275, 4,834,306, 4,848,693, and 4,846,418, a leader-advancing cassette has been proposed in which the photographic film is initially contained completely within the cassette, and the leader is advanced to the passage mouth upon rotation of the spool in the direction of unwinding the photographic film. In such a cassette, rotation of the spool by a mechanism of the camera causes the leader to advance to the outside of the cassette shell through the passage mouth.
If a pile fabric having pile threads is used as light-trapping ribbons, the directions of pile threads can become unfavorably disorganized during manufacturing processes such as dying and brushing. In some cases, pile threads will be, possibly irrecoverably, inclined in the film rewinding direction, i.e., toward the inside of the cassette shell.
With a leader-advancing cassette, whose leader is positioned initially within the cassette, the leader must advance through the passageway against any resistance due to the light-trapping ribbons therein. If there is a considerably large resistance, the photographic film may be bent within the cassette, and rotation of the spool might fail to advance the leader. Also, a battery powering the advance mechanism of the camera will be quickly consumed if the resistance to film advancement is high, because a relatively large torque is required to rotate the spool.